1. Field of the Invention
The present invention is directed toward wireless communication systems, and particularly toward improved use of the limited supply of channels in such systems.
2. Description of the Related Art
Wireless communication systems are, of course, widely used throughout the world today. In a typical system, cellular telephone phone systems are used to permit communication to mobile terminals which may move in and between different cells covered by different radio base stations. Current cellular systems such as GSM, IS-95 (CDMA) and IS-136 (D-AMPS) provide coverage in homes in the same way they provide coverage when the mobile terminal is on the road (i.e., all calls in a cell, including cellular telephone calls while at home, use cellular traffic channels). However, there is a limited supply of available channels, which supply is burdened more and more as the number of cellular subscribers continues to grow. Cellular operators typically add capacity to meet the growing number of subscribers by adding more traffic channels, if available, or more cells if not. Adding cells when sufficient traffic channel frequencies are not available involves reducing the size of surrounding cells, and is very expensive to do, since each new cell not only requires land or space for the cell tower and equipment, but also data lines to connect the cell to the mobile switching center as well as the equipment and installation costs.
One solution which has been proposed is to use an extremely low power home base station to handle cellular calls on mobile terminal made at home. The home base station would provide control channels and traffic channels within the operator's frequency band, but the power output would be so low as to not interfere with the larger surrounding cells. When a mobile terminal roams into the coverage of the home base station (i.e., is at home), it would switch to the home base station control channel to receive all services via the home base station. However, while this proposed solution provides more capacity (by reducing the load on the cells by switching some calls to the home base station), it introduces other problems. For example, such home base stations are fairly complicated and are themselves relatively expensive. Also, though the air interface of some standards has been designed to support such home base stations, it is not clear how the home base stations would tie back into the mobile switching center, since connecting individual home base stations to the mobile switching center like radio base stations does not scale well, since the radio base station interface with the mobile switching center is designed for a small number of radio base stations each with a large number of traffic channels whereas this solution would generate a large number of home base stations each using only a small number of traffic channels. Further, while the home base stations of this solution could connect directly to the public switched telephone network (PTSN) somewhat like a cordless telephone, this solution provides revenue to the PTSN operator at the expense of the cellular system operator.
The present invention is directed toward overcoming one or more of the problems set forth above.